Novel aluminum fluoride catalyst and process for hydrofluorinating acetylene using same

ABSTRACT

Process for hydrofluorinating acetylene which comprises reacting acetylene with hydrogen fluoride in the vapor phase and in the presence of Epsilon -aluminum fluoride at a temperature from about 200*C to about 380*C to produce vinyl fluoride and 1,1difluoroethane, said Epsilon -aluminum fluoride is being prepared by evaporating an aqueous hydrofluoric acid solution of aluminum fluoride to dryness under vacuum at a temperature from 30*to 120*C optionally followed by heating the resulting product at a temperature from 120* to 500*C.

United States atent n91 Wada et al.

l 1March 13, 1973 I NOVEL ALUMINUM FLUORIDE CATALYST AND PROCESS FOR HYDROFLUORINATING ACETYLENE USING SAME [75] Inventors: lliroyuki Wada, Kyoto; Yasumasa Kawakami; Tutomu Kamihigoshi, both of Osaka, all of Japan [73] Assignee: Daikin Kogyo Co., Ltd., Osaka-fu,

, Japan [51] Int. Cl ..C07c 17/08 [58] Field of Search ..260/653.4, 653.6; 252/442 [5 6] References Cited UNITED STATES PATENTS 3,432,441 3/1969 Gardner ..260/653.4

Primary Examiner-Howard T. Mars Assistant Examiner-Joseph A. Boska Att0rneyJacobs & Jacobs [57] ABSTRACT Process for hydrofluorinating acetylene which comprises reacting acetylene with hydrogen fluoride in the vapor phase and in the presence of e-aluminum fluoride at a temperature from about 200C to about 380C to produce vinyl fluoride and 1,1- difluoroethane, said e-aluminum fluoride isbeing prepared by evaporating an aqueous hydrofluoric acid solution of aluminum fluoride to dryness under vacuum at a temperature from 30to 120C optionally followed by heating the resulting product at a temperature from 120 to 500C.

8 Claims, 2 Drawing Figures PATENTEDHAR 1 3|975 ZOEHEOmQd mI F3 855KB 3255 TEMPERATURE (c)' IT 5 O 5 0 ll TEMPERATURE (C) NOVEL ALUMINUM FLUORIDE CATALYST AND PROCESS FOR HYDROFLUOIRHNATING ACETYLENE USING SAME This is a division of my copending application Ser. No. 770,337 filed Oct.24, 1968.

This invention relates to a novel aluminum fluoride catalyst (i.e. e-aluminum fluoride) and a process for hydrofluorinating acetylene using the same.

The term e-aluminum fluoride herein used is intended to mean e aluminum fluoride, ta -aluminum fluoride and e -aluminum fluoride, and their intertransition forms, inclusively.

It is well known that vinyl fluoride, CH =CHF, and l,1difluoroethane, CH CHF are produced by reacting acetylene with hydrogen fluoride in the vapor phase and in the presence of an aluminum fluoride catalyst. There are several crystalline forms of aluminum fluoride, and some of them are useful as hydrofluorination catalysts. Aluminum fluoride first disclosed in U.S. Pat. No. 2,471,525 was named as a-aluminum fluoride in the patents issued thereafter, and B-aluminum fluoride and 'y-alurninum fluoride were disclosed respectively in U.S. Pat. Nos. 3,178,483 and 3,178,484. S-Aluminum fluoride was also disclosed in Japanese Patent Publication No. 2,252/1967 corresponding to U.S. Pat. Nos. 3,178,483 and 3,178,484 and US. Pat. applications Ser. Nos. 236,410 and 236,41 1, both filed on Nov. 8, 1962. These aluminum fluorides are easily characterized by their X-ray diffraction patterns and distinguished one another. They are obtained by dehydrating under selective temperatures a-aluminum fluoride trihydrate and fl-aluminum fluoride trihydrate which are prepared by precipitating from an aqueous hydrofluoric acid solution of aluminum or aluminum oxide. They have a high catalytic activity in the reaction of acetylene with hydrogen fluoride, offer a high conversion rate of acetylene and reduce the yields of tars and other by-products. However, in commercial production, their catalyst life is still unsatisfactory.

it has now been found that a crystalline form of the aluminum fluoride obtained by evaporating an aqueous hydrofluoric acid solution of aluminum fluoride at a regulated temperature, optionally followed by heating the product at a selected temperature is distinguished from anyone of known crystalline forms of aluminum fluoride by X-ray diffraction pattern. It has also been found that such aluminum fluoride, named as e-aluminum fluoride, has a longer catalyst life, compared with known aluminum fluorides (i.e. a-aluminum fluoride, B-aluminum fluoride, 'y-aluminum fluoride, 5- aluminum fluoride) used as the catalyst for hydrofluorination of acetylene. The present invention is based on these findings.

Accordingly, a basic object of the present invention is to embody a novel crystalline form of aluminum fluoride useful as a catalyst for hydrofluorination of acetylene. Another object of this invention is to embody an aluminum fluoride catalyst having a long catalyst life in the reaction of acetylene with hydrogen fluoride. A further object of the invention is to embody a process for hydrofluorinating acetylene using e-aluminum fluoride. These and other objects will be apparent to those conversant with the art to which the prevent invention pertains from the subsequent description.

The c-aluminum fluoride of the present invention is a new crystalline form of aluminum fluoride. It has an excellent catalytic activity, offers a high conversion rate of acetylene and possesses a long catalyst life in the reaction of acetylene with hydrogen fluoride.

The e-aluminum fluoride involves e -aluminum fluoride, e -aluminum fluoride and e -aluminum fluoride, which convert in turn, and intertransition forms of them. Each of e -aluminum fluoride, e -aluminum fluoride and e -aluminum fluoride is stable at a selected temperature range and has a different crystalline structure which is clearly characterized by its X- ray diffraction pattern. The diffraction angles, spacings and intensities of the X-ray diffraction patterns ofqaluminum fluoride, e -aluminum fluoride and e -aluminum fluoride are given in Tables I, II and III, respectively.

Table I. Diffraction angles, spacings and intensities of e -aluminum fluoride.

Diffraction angle Spacing intensity 2 0 (degree) a (A) 8.1 10.915 vst 18.8 4.719 st 24.8 3.590 vst 26.4 3.370 st 28.1 3.175 st 31.2 2.866 vw 33.1 2.706 vw 34.5 2.599 vw 38.3 2.350 vw 45.7 1.895 w 50.8 [.797 st 51.5 1.774 w 54.6 1.680 w Note: st strong; w weak; v very.

Table II, Diffraction angles, spacings and intensities of e -aluminum fluoride.

Diffraction angle Spacing intensity 2 6 (degree) a (A) 10.2 8.672 vst 18.8 4.719 st 20.4 4.353 m 23.7 3.754 w 24.9 3.561 vst 28.1 3.175 st 30.7 2.912 vw 47.5 1.914 vw 50.8 1.797 in Note: st strong; in medium; w weak; v very.

Table 111. Diffraction angles, spacings and intensities of e -aluminum fluoride.

Difl'raction angle Spacing intensity 2 0 (degree) (A) 25.0 3.561 vst Note: st strong; in medium; v very.

As shown in Tables I, [I and III, e -aluminum fluoride has relatively strong X-ray diffraction peaks at angles of diffraction of 2 0 8.l, l8.8, 24.8, 26.4, 28.1 and 50.8", e -aluminum fluoride has at 2 0 102, 18.8", 237, 24.9, 28.1 and 50.8, and e -aluminum fluoride has at 2 0=11.8, l8.8, 22.3, 25.0", 28.1" and 51.4.

The e-aluminum fluoride of this invention is obtained by dissolving an aluminum compound, i.e. aluminum fluoride itself or a compound which is reacted with hydrogen fluoride to form aluminum fluoride such as aluminum oxide, aluminum hydroxide or aluminum chloride, in an aqueous solution of hydrogen fluoride and, after removing the precipitate when produced, evaporating the resultant hydrofluoric acid solution of aluminum fluoride to dryness under a temperature of from 30 to 120C (preferably from 90 to 100C) to form e -aluminum fluoride, optionally followed by heating the e -aluminum fluoride at a temperature from l20 to 500C to give e -aluminum fluoride or e -aluminum fluoride, or their intertransition form. c -Aluminum fluoride gradually changes to e -aluminum fluoride when heated above 120C, and this transition proceeds quite smoothly at a temperature above 140C. e -Aluminum fluoride begins to form e -aluminum fluoride at a temperature above 180C, and 6;,- aluminum fluoride is converted to a-form when heated above 500C, the aluminum fluoride in a-form being of less catalytic activity. For the preparation of e -aluminum fluoride, it is thus preferred to heat e,-aluminum fluoride at a temperature from 140 to 200C. For the production of e -aluminum fluoride, it is favorable to heat e -aluminum fluoride at a temperature from 240 to 400C.

The transition e-aluminum fluoride as described above is confirmed from the variation of the peaks of X-ray diffraction between the angles of diffraction of 2 6 8 and of 2 12. e -Aluminum fluoride has a strong peak at a diffraction pattern of 2 0 8.0", which disappears in the X-ray diffraction pattern of e -aluminum fluoride. ta -Aluminum fluoride has a strong peak at 2 0 10.2. In the intertransition state from 6,- form to e -form, medium peaks are observed at both 2 0 8.l and 102. e -Aluminum fluoride has a peak at 2 0=11.8 but loses peaks at 2 6 8.1 and 10.2". In the intertransition state from e -form to e -form, it is observed that the peak at 2 0 10.2 moved gradually to 2 0 1 l.8, but the peak has broad width and, therefore, the change of the peaks is not clearly acknowledged. Table IV shows the relationship between the heating temperature of e -aluminurn fluoride and the diffraction angle Table IV. Heating temperatures of e -aluminum fluoride and diffraction angles.

Heating temperature Diffraction angle at 2 0 l0l 2 de rec (ac) s 200 10.2 220 10.4 250 10.6 270 11.0 300 11.8 400 11.8

Note: range of error, i C.

When q-aluminum fluoride is subjected to differential thermal analysis in which 30 milliligrams of the specimen is heated at an elevation rate of 10C per minute, it affords the endothermic change as shown in FIG. 1. The thermogravimetric analysis of e -aluminum fluoride is carried out at an elevation rate of 5C per minute with 100 milligrams of the specimen, and the curve taken from thermobalance is shown in FIG. 2. These thermometric test results are peculiar to e-aluminum fluoride and never observed in known crystalline crystalline forms of aluminum fluoride.

From the above results and by the quantitative analysis of water in e-aluminum fluoride, it is presently concluded that e -aluminum fluoride, e -aluminum fluoride and ta -aluminum fluoride correspond to A1F -L5 H 0, AlF -0.5 H 0 and AW: (anhydrous), respectively.

Still, e -alurninum fluoride can be converted to e,- aluminum fluoride by contacting with a liquid which has a dehydrating effect such as anhydrous methyl alcohol or anhydrous trifluoroacetic acid.

According to the present invention, acetylene is reacted with hydrogen fluoride in the vapor phase and in the presence of e-aluminum fluoride at a temperature from about 200C to about 380C to produce vinyl fluoride and 1,1-difluoroethane.

In the reaction, any crystalline form of e-aluminum fluoride (i.e. e -aluminum fluoride, c -aluminum fluoride, e -aluminum fluoride, their intertransition form) may be used alone or in mixture as the catalyst. The form of the catalyst may be in a conventional one such as powder, pellets or on a carrier (e.g. activated carbon, alumina).

During the reaction where a temperature from about 200C to about 380C is applied, e -aluminum fluoride is converted to e -form, which is further changed partially to e -form. Therefore, the catalytically active form of e-aluminum fluoride may be considered as the mixture of e -form and e -form or the intertransition form from e -form to e -form.

The e-aluminum fluoride catalyst is placed in a reactor so as to contact the same with a flow of acetylene and hydrogen fluoride.

The reactor may be of horizontal type, vertical type or fluidized-bed type. Any materials which stand hydrogen fluoride at the reaction temperature may be used for the reactor. Examples of such materials are mild steel, stainless steel, nickel, Monel and Inconel. For heating the reactor, any conventional method may be applied.

The reactor and the catalyst are heated to a desired reaction temperature, and a mixture of acetylene and hydrogen fluoride, which may be pre-heated, is fed through the catalyst. The gaseous product from the reactor consisting of vinyl fluoride, 1,1-difluoroethane, unreacted acetylene and hydrogen fluoride, and some of by-products, is first bubbled through water and aqueous alkali and then separated into its constituents by conventional distillation. Acetylene may be alternatively separated by means of solvent extraction or utilizing copper acetylide reaction.

The reaction temperature ranges from about 200C to about 380C, preferably from about 220C to about 300C. At temperatures below about 200C, the conversion rate of acetylene is low, and above about 380C the formation of by-products increases.

The reaction pressure is not critical, but it is preferred to operate at atmospheric pressure for ease of operation.

For the production of vinyl fluoride, the preferred molar ratio of acetylene to hydrogen fluoride ranges from about 1 z 1.1 to about 1 1.6, and for 1,1- difluoroethane, from about 1 2.2 to about 1 3.0.

The space velocity of acetylene may be selected appropriately from the range where the high conversion is obtained.

As well known, vinyl fluoride thus obtained is a monomer for producing useful polymers, especially polyvinyl fluoride. 1,1-Difluoroethane is'useful as a refrigerant, propellant and as an intermediate for preparing other valuable products such as vinyl fluoride, vinylidene fluoride and chlorodifluoroethane.

Practical and presently preferred embodiments of the present invention are illustratively shown in the following examples.

EXAMPLE 1 In a polyethylene beaker, 500 grams of aluminum hydroxide was added slowly to 1,100 milliliters of 55 percent hydrofluoric acid with stirring and water-cooling of the acid. After all of the aluminum hydroxide was completely dissolved, the acid solution was evaporated under vacuum at 80C. The aluminum fluoride thus obtained was identified as e -aluminum fluoride by X-ray diffraction.

The e -aluminum fluoride was heated in a muffle furnace at 140C for 2 hours. The X-ray diffraction pattern of the obtained aluminum fluoride showed the mixture of e -form and e -form, and the substance is assumed to be an intertransition state from e,-form to a,- form.

The aluminum fluoride was further heated at 180 to 200C for 3 hours. The aluminum fluoride thus heattreated was identified as e -aluminum fluoride.

The e -aluminum fluoride was heated at 240 to 260C for 2 hours. The X-ray diffraction angle of the obtained aluminum fluoride was 10.6. The substance is assumed to be an intertransition state from e -form to e -form.

The aluminum fluoride was further heated at 300C for 2 hours. The aluminum fluoride thus obtained was e -form. Chemical analysis showed that the molecular formula of e -aluminum fluoride was AlF EXAMPLE 2 In a polyethylene beaker, 1,000 grams of powdered anhydrous aluminum chloride was added into 1,500 milliliters of 55 percent aqueous hydrofluoric acid with stirring and water-cooling. After filtering the precipitate, the acid solution was evaporated to dryness on a water bath. The obtained aluminum fluoride was identified as e -aluminum fluoride by X-ray diffraction.

EXAMPLE 3 In a polyethylene beaker, 5 grams of q-aluminum fluoride was added into 500 milliliters of anhydrous methyl alcohol. After stirring at room temperature for 50 hours, the methyl alcohol was removed under vacuum. The X-ray diffraction pattern of the obtained aluminum fluoride showed that almost of e -aluminum fluoride was converted to e -form.

EXAMPLE 4 A tubular stainless steel reactor of 27 millimeters in inner diameter was mounted vertically in an electrically heated molten salt bath, and 60 grams of pelletized e aluminum fluoride obtained in accordance with Example 1 was filled in the reactor. A gaseous mixture of anhydrous hydrogen fluoride and acetylene (molar ratio of l-lF/C H 2/1) was fed into the reactor at a reaction temperature of 260C and a space velocity of milliliters of acetylene/gram of catalyst/hour (at Standard Temperature and Pressure) from the top of the reactor. The effluent gaseous product from the bottom of the reactor was scrubbed through water and aqueous alkali to remove hydrogen fluoride, dried through calcium chloride and then analyzed by gas chromatography to calculate the conversion rate of acetylene and the yields of the products.

The acetylene used this run was purified by sulfuric acid for removal of acetone.

For comparison, the same procedures were repeated using a-aluminum fluoride and 'y-aluminum fluoride.

The results are shown in Table V.

Table V. Comparison of catalyst life of aluminum fluoride.

Form of AlF, Conversion rate of acetylene (96) 10 hrs. 50 hrs. 100 hrs. hrs. 200 hrs. a 99 99.5 99.1 98.3 98.6 7 98.7 98.4 98.1 92.2 30.9 a 97.1 92.2 28.3

In each run, the molar ratio of vinyl fluoride in the product was about 25 percent, and that of 1,1- difluoroethane was about 75 percent. When the conversion rate of acetylene was reduced, the formation of vinyl fluoride was increased.

EXAMPLE 5 As in Example 4, the reaction was effected but using e -aluminum fluoride obtained in accordance with Example l in place of e -aluminum fluoride. The conversion rates of acetylene after 10 hours and 200 hours were respectively 99.1 percent and 98.7 percent. No practical reduction of the catalytic activity of e-aluminum fluoride was observed.

What is claimed is:

1. A process for hydrofluorinating acetylene which comprises reacting acetylene with hydrogen fluoride in the vapor phase and in the presence of e-aluminum fluoride selected from the group consisting of e -aluminum fluoride having the empirical formula AlF 1.5 H 0 and being characterized by an X-ray diffraction pattern with peaks at diffraction angles 8.1 (very strong), l8.8 (strong), 24.8 (very strong), 26.4 (strong), 28.1 (strong) and 50.8 (strong) and with spacings in A of 10.915A, 4.719A, 3.590A, 3.370A, 3.175A and 1.797A respectively, for each angle noted, e -aluminum fluoride having the empirical formula All -0.5 H 0 and being characterized by an X-ray diffraction pattern with peaks at diffraction angles l0.2 (very strong), 18.8 (strong), 23.7 (weak), 24.9" (very strong), 28.1 (strong) and 50.8 (medium) and with spacings in A of 8.672A, 4.719A, 3.754A, 3.561A, 3.175A and 1.797A respectively, for each angle noted, and e -aluminum fluoride having the empirical formula All: and being characterized by an X-ray diffraction pattern with peaks at diffraction angles 11.8 (medium), 18.8 (medium), 22.3 (medium), 250' (very strong), 28.1 (medium) and 5l.4 (medium) and with spacings in A of 7.499A, 4.719A, 3.986A, 3.561A, 3.175A and 1.777A, respectively,for each angle noted, and mixtures thereof at a temperature from about 200C to about 380C to produce vinyl fluoride and 1 ,1 -difluoroethane.

2. A process for hydrofluorinating acetylene according to claim 1 wherein 1.1 to 3.0 mol of hydrogen fluoride per 1 mol of acetylene is subjected to the reaction.

3. A process according to claim 1, wherein the e-aluminum fluoride is e,-aluminum fluoride having the empirical formula All- 1.5 H 0 and being characterized by an X-ray diffraction pattern with peaks at diffraction angles 8.1 (very strong), 18.8 (strong), 24.8 (very strong), 26.4 (strong), 28.l (strong) and 50.8 (strong) and with spacings in A of 10.915A, 4.7l9A, 3.590A, 3.370A, 3.175A and 1.797A for each angle noted.

4. A process according to claim 1, wherein the e-aluminum fluoride is e -aluminum fluoride having the empirical formula All -0.5 H 0 and being characterized by an X-ray diffraction pattern with peaks at diffraction angles l0.2 (very strong), 18.8 (strong), 23.7 (weak), 24.9 (very strong), 28.l (strong) and 50.8

5. A process according to claim 1, wherein the e-aluminum fluoride is e -aluminum fluoride having the empirical formula AIR, and being characterized by an X- ray diffraction pattern with peaks at diffraction angles ll.8 (medium), l8.8 (medium), 223 (medium), 25.0" (very strong), 28.l (medium) and 51.4" (medium) with spacings in A of 7.499A, 4.7l9A, 3.986A, 3.56lA, 3.175A and 1.777A, respectively, for each angle noted.

6. A process for hydrofluorinating acetylene according to claim 3 wherein 1.1 to 3.0 mol of hydrogen fluoride-per 1 mol of acetylene is subjected to the reaction.

7. A process for hydrofluorinating acetylene according to claim 4 wherein 1.1 to 3.0 mol of hydrogen fluoride per 1 mol of acetylene is subjected to the reaction.

8. A process for hydrofluorinating acetylene according to claim 5 wherein 1.1 to 3.0 mol of hydrogen (medium) with spacings in A of 8672A, 4719A, fluoride per 1 mol ofacetylene is subjected to the reac- 3.754A, 3.561A, 3.l75A and 1.797A, respectively, for each angle noted.

i =0: a: w 

1. A process for hydrofluorinating acetylene which comprises reacting acetylene with hydrogen fluoride in the vapor phase and in the presence of epsilon -aluminum fluoride selected from the group consisting of epsilon 1-aluminum fluoride having the empirical formula AlF301.5 H20 and being characterized by an X-ray diffraction pattern with peaks at diffraction angles 8.1* (very strong), 18.8* (strong), 24.8* (very strong), 26.4* (strong), 28.1* (strong) and 50.8* (strong) and with spacings in A of 10.915A, 4.719A, 3.590A, 3.370A, 3.175A and 1.797A respectively, for each angle noted, epsilon 2-aluminum fluoride having the empirical formula AlF3.0.5 H20 and being characterized by an X-ray diffraction pattern with peaks at diffraction angles 10.2* (very strong), 18.8* (strong), 23.7* (weak), 24.9* (very strong), 28.1* (strong) and 50.8* (medium) and with spacings in A of 8.672A, 4.719A, 3.754A, 3.561A, 3.175A and 1.797A respectively, for each angle noted, and epsilon 3-aluminum fluoride having the empirical formula AlF3 and being characterized by an X-ray diffraction pattern with peaks at diffraction angles 11.8* (medium), 18.8* (medium), 22.3* (medium), 25.0* (very strong), 28.1* (medium) and 51.4* (medium) and with spacings in A of 7.499A, 4.719A, 3.986A, 3.561A, 3.175A and 1.777A, respectively, for each angle noted, and mixtures thereof at a temperature from about 200*C to about 380*C to produce vinyl fluoride and 1,1-difluoroethane.
 2. A process for hydrofluorinating acetylene according to claim 1 wherein 1.1 to 3.0 mol of hydrogen fluoride per 1 mol of acetylene is subjected to the reaction.
 3. A process according to claim 1, wherein the epsilon -aluminum fluoride is epsilon 1-aluminum fluoride having the empirical formula AlF3.1.5 H20 and being characterized by an X-ray diffraction pattern with peaks at diffraction angles 8.1* (very strong), 18.8* (strong), 24.8* (very strong), 26.4* (strong), 28.1* (strong) and 50.8* (strong) and with spacings in A of 10.915A, 4.719A, 3.590A, 3.370A, 3.175A and 1.797A for each angle noted.
 4. A process according to claim 1, wherein the epsilon -aluminum fluoride is epsilon 2-aluminum fluoride having the empirical formula AlF3.0.5 H20 and being characterized by an X-ray diffraction pattern with peaks at diffraction angles 10.2* (very strong), 18.8* (strong), 23.7* (weak), 24.9* (very strong), 28.1* (strong) and 50.8* (medium) with spacings in A of 8.672A, 4.719A, 3.754A, 3.561A, 3.175A and 1.797A, respectively, for each angle noted.
 5. A process according to claim 1, wherein the epsilon -aluminum fluoride is epsilon 3-aluminum fluoride having the empirical formula AlF3 and being characterized by an X-ray diffraction pattern with peaks at diffraction angles 11.8* (medium), 18.8* (medium), 22.3* (medium), 25.0* (very strong), 28.1* (medium) and 51.4* (medium) with spacings in A of 7.499A, 4.719A, 3.986A, 3.561A, 3.175A and 1.777A, respectively, for each angle noted.
 6. A process for hydrofluorinating acetylene according to claim 3 wherein 1.1 to 3.0 mol of hydrogen fluoride per 1 mol of acetylene is subjected to the reaction.
 7. A process for hydrofluorinating acetylene according to claim 4 wherein 1.1 to 3.0 mol of hydrogen fluoride per 1 mol of acetylene is subjected to the reaction. 